RFR (S): 8140343: SEGV in DirectivesStack::getMatchingDirective

Nils Eliasson nils.eliasson at oracle.com
Wed Oct 28 09:15:37 UTC 2015

Still open for review.


On 2015-10-24 10:49, Nils Eliasson wrote:
> On 2015-10-23 22:39, Christian Thalinger wrote:
>>> On Oct 22, 2015, at 11:03 PM, Nils Eliasson 
>>> <nils.eliasson at oracle.com> wrote:
>>> Hi all,
>>> This fixes a bug when using a compiler that doesn't have compiler 
>>> directives. This is a temporary fix using the default directive for c1.
>> What are the default directives for C1 and C2?  This fix is for JVMCI 
>> compilers and JVMCI compilers can only replace C2 in a tiered 
>> configuration.  Depending on what they are, wouldn’t it make more 
>> sense to use C2’s default directives?
> The default directive is a directive that is always installed, always 
> enabled and contains all the default values from vmflags and compile 
> commands. This is the directive all compilations are using if no 
> additional directives are installed.
>>> In the future permanent fix all compilers will have directives by 
>>> default.
>> How would that look like?
> Long story. It is an internal implementation detail to the structure 
> of compiler directives. Right now there is a bit of an overhead adding 
> a new compiler, even if only a single flag is used. The idea is to 
> have all directives contain all flags for all compilers - it might 
> sound expensive but will actually be more efficient. The most common 
> use case is only having the default directive, and in this case the 
> common flags wouldn't have to be duplicated for each compiler. The 
> profit in the JVMCI case is that all the common flags are valid and 
> usable without any workaround. The improvement is straightforward and 
> wont affect any use site but is big enough not to be the fix of this bug.
> //Nils
>>> bug: https://bugs.openjdk.java.net/browse/JDK-8140343
>>> webrev: http://cr.openjdk.java.net/~neliasso/8140343/webrev.01/
>>> Please review,
>>> Nils

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